Aircraft power plant for high altitude flight



Oct. 23, 1945. BQULET 2,387,560

AIRCRAFT POWER PLANT FOR HIGH ALTITUDE FLIGHT Filed Nov. 15, 1939 p r. M/-

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ALTITUDIIHG Georges lollet,

veltcdinthc ,Applitationflov'ember Novel:

rum-r roamcn Allen Guam 1, 1.3.. Serial No. m be: as, im

40mm. (CI. 50-13) Q My present invention has for its object to provide an aircraft internal'combustion engine for flight at high altitude, more especially in the stratosphere, which is more particularly intended for long distancesand has a low specific consumption, which is ensured by its cycle of op-' eration, independently of the other known means thatmay likewise act to decrease such consumption (adjustable richness carburettor, injection of gasoline into the pipes or into the cylinder, injection of additional liquid, special chamber, etc.), said low consumption existing at its normal altitude of operationtand preferably also under all conditions of operation at any intermediate altitude.

A further object of my, invention is to provide an aircraft engine having a substantially constant power at all altitudes.

A further object of my inventionis to provide in the usual combination of an engine of the explosion type and a system of air compression an engine of the high volumetric ratio type (higher than 8 to 1) and undercharged, that is to say wherein the pressure p'o atthe end of the intake stroke with the throttle wide open is lower than the atmospheric pressure on the ground. This pressure po is dependent on the octane index of the fuel that can be employed in normal operation at the altitudes in question.

The undercharging may be obtained either by means of a throttling of the intake, or preferably by means of a distribution which is adjustable in flight, or by means of unequal strokes of the piston, etc.

The adjustable distribution enables when on the ground a small overlap to be obtained of the periods of closing of the exhaust and of open- Similarly, the delay might be considered in engines provided with carburettor: with a buiier, chamber between the cylinders and the members controlling the intake. 7 Similarly a system called after-charging might be considered, in which the intake at the pressure Z1 takes place at that partof the end of the intake stroke during which the piston only under- On the other hand, at the'instant when the quick climb stops and when the flight continues with a very gentle climb, as the aeroplane becomes lighter, the mechanical compressor can be stopped and will 'then onlyact as a conveyor, or it can be cut out of the system and its action replaced by that of the dynamic pressure in the shaft. It will be reintroduced into the. system when its action becomes necessary again, that is to say on the level located below the end of constant intake pressure altitude, by an amount corresponding to its compression ratio.

In order to enable the invention to be better understood, reference is made to the following description'and the appended drawing illustrating application of the invention, wherein:

ing of the intake, and a substantially greater intake valve or valves or of the intake distributor or distributors) will be late, thereby driving the air into one or other of the pipes, preferably the intake pipe, the adjustment becoming normal again at the altitude Z1 called reference'altitude.

Figure 1 is a diagram of a cycle of operation.

Figs. 2 to 5 show partial diagrams at different altitudes of under-charged engines.

Fig. 6 shows diagrammatically, by way of a non-limitative example, an embodiment provided with the various features mentioned above.

Figs. 7 and 8 show diagrammatically a modified embodiment.

In the complex embodiment shown in Fig. 6, the basic combination of the whole arrangement is formed by that of an under-charged engine shown diagrammatically at l and by a compressor II. The general cycle of the type of engine i is shown in Fig. 1.

Fig. 1 shows the theoretical diagram corresponding to the (adiabatic) compression stroke (AB) and the (adiabatic) expansion stroke (CD). This diagram remains the same whatever he. the manner in which the under-charging is effected.

The consequences of two different manners of effecting the under-charging are shown in Figs.

2 to 5 which are figurative diagrams of the intake and exhaust strokes. Figs. 2 and 3 relate ot-rrcii toan engine which is under-charged by throttling the intake, Figs. 4 and 5, an engine which is under-charged by closing the intake valve long before the end of the stroke of the piston.

Fig. 2 shows the operating diagram at the altitude at which the end of intake pressure p'. prevails,,whereas.the.diagram ofFig. 3. is that of the operationat the altitude o. It will be seen:

that in this latter case there exists a work of suction represented by the area AELJ which is far from being negligible This loss has almost entirely' disappeared in the diagram of'Fig. 5in which the under-charging is obtained by closing the intake valve at a point E2 corresponding to an intermediate position II of the piston in itsintake stroke which is chosen in such a manner that the mass introduced expands during the remainder oi the intake stroke according to the adiabatic asa'asoo containing one of the'wheels 21. 28. 'It is into i the compartment of the wheel 21 which drives the compressor II that the exhaust pipe I leads and said compartment is provided with a direct exhaust pipe 30 controlled by a valve 8|. The compartment of the wheel 2! is likewise provided with anexhaust pipe 22, opening directly into the atmosphere, without a. valve, and' it communicates with the other compartment. Finally,

on the exhaust pipe I is arranged between the engine and the turbines an exhaust pipe 30 controlled by a" valve 3l which is actuated by a,

manometric capsule M4 subjected to the pressure curve E: A which is as close as possible to the adiabatic curve A E of the compression stroke of the general cycle (Fig. 1,). The diagram of Fig. 4 is equivalent to that ofFig. 2, save that this particular manner of undercharging the engine by varying the instant of closing the intake valve enables the intake valve to be closed at the altitude Po only after the closing of the exhaust valve and thereby enables a scouring to be obtained which has the eifect of increasing the power owing to the fact that the cylinder is entirely cleansed of burnt gases and is consequently filled with a more considerable mass of fresh gas than when burnt gases remain; furthermore, the volumetric ratio of the combustion chamber can the closing of the exhaust valve.

be made higher owing to the cooling of thecombustion chamber by the fresh gases and to the lower temperature of the mass at the end of the I intake. V I

In this embodiment of Fig. 6, the engine I is of the high volumetric compression type, for example higher than 9 to 1 and has two valveoperating camshafts angularly displaceable during the operation of the engine, for example by means of a device of the type described in my Patent No. 1,787,717 dated Jan. 6, 1931. 4 designates the intake pipe, 5 the intake valve, 6 the exhaust valve, I the exhaust pipe, 8 a usual supply carburettor and 9 the usual butterfly valve for con-trolling the power of the engine; I0 is an air intake located on the intake pipe after a compressor II which is mechanically driven by the motor I; I2 is a throttle valve for the air intake l0 and is controlled by a manometric capsule M and subjected to the influence of the pressure prevailing in the intake pipe 4. On the intake pipe of the compressor II which is connected through a pipe l5 and a cooler I6 to the delivery pipe of another compressor I1, is arranged at 18 an air intake direct from the atmosphere, which air intake is controlled by a valve I0 controlled by a-manometric capsule M: and subjected to the pressure that prevails in the pipe l5 as shown.

Said compressor I1 has its intake pipe connected through a pipe 20 and a cooler 2| to the delivery pipe of another compressor 22, and 23 designates a direct air intake arranged on the intake pipe of the compressor l1; avalve 24 controls s'aidair intake 23 and is actuated by a manometric capsule M3 subjected to the pressurevin the pipe 20 as shown. The air intake of the compressor 22 is shown at 25.

The compressors I1, 22 are each respectively mounted on the shaft of a turbine 21, 28. Sam turbines are coaxial and their outer case is common but divided into two compartments each prevailing in the exhaust pipe I. 1

The operation of this arrangement is asfolperiods of the intake valves] and of the exhaust valves, by means of the angularly displaceable camshaft (not shown); the settings from the up per dead centre are forexample +0 and for the'opening and the closing of the intake valve 5 and and +10 for the opening and I The exhaust take place through the 'pipe .36, the valve 31 being wide open. Up to the altitude Z1, the intake pressure remains the. same by an appropriate adjustment of the angularly displaceable camshaft. The setting at Z1 is for example -10 and +225 for the intake valve 5 and +135 and +30 for the exhaust valve 5. At Z1 the valve 12 is closed by hand. The valve l2 and the valves I 9 and 24 are closed gradually and they are arranged to open again if excessive pressure appears. At the same time, the mechanical compressor H is started if same is not constantly driven by the engine. In practice, the compressor H need not be operated until the aircraft has reached a certain altitude, but no difilculty would be encountered if this compressor were operated constantly, because at low altitudes the vent i2would discharge sufficient air to maintain the desired pressure on the engine. Vent valves 3| and 31 are operated similarly to the valve ii. The suction then takes place when the compressor l I is started, through the 7 air intake l8 and the valve l9 more or less throttles said air intake so that the intake pressure always remains equal to 405 mm. From an altitude Z: (6,500 metres for instance) the closing of the valve 31 starts and a portion of the exhaust gases passes through the turbine 21, thereby actuating the compressor l!- which drives air 1 through the pipe l5 but at a pressure which is that determined by the valve i9. From the altitude 'Ze (6,500 metres) the cycle of the engine remains completely and the valve 31 is completely closed;'

the exhaust is then effected completely through the turbine 21 and the pipe 30, while the air intake takes place through the pipe 23 which is suitably throttled by the valve 24 so thatthe intake exhaust then takes place through the two wheels II and in series and the pipe 32; then at Z: the valve 24 closes. so that the supply of air to the engine is effected through the pipe and the passage of the air successively through the three compressors 22, I1 and II, which restore the measured 405 mm. up to an altitude Z4 (15,000 metres for instance).

The power of the engine I therefore remains substantially constant between 0 and 15,000 metres. Above Z4 (15,000 metres) there is a decrease of power of the engine.

In the modified embodiment of Fig. 7, the englue is provided, in addition to its normal exhaust valve ll, with a special exhaust valve ll, or with a similar device called "1) device, that is to say which opens astride on the lower dead centre. at which instant the piston is nearly stationary and opens into a pipe leading to a variable pressure turbine 42. The valve 4| is controlled in the usual manner by means of a camshaft. The valve may be controlled as described in my patent, No. 1,787,717, supra, in order to be adjustable in flight. Cams l4 and on the camshaft 43 may be provided to operate the valves 40 and ll, respectively, and a cam 45 to operate the intake valve I. The auxiliary exhaust valve ii is arranged to be open during the initial portion or the exhaust stroke of the piston, the'main exhaust valve 4. being open during the remainder of the exhaust stroke.

Fig. 8 gives an example of such a control: in thisexample, the pui'f valve 41 opens only from A to B at the beginning of the exhaust stroke and then recloses. The normal valve 40 open from BtoCatgroundieveibutfromBtoDatan altitude of 5,000 meters.

0! course, the invention is in no way limited to the details of construction illustrated or described, which have only been given by way of example. Thus, the numerical data given above are in no way absolute and the plant described could be designed to operate between other limits of altitude without thereby exceeding the scope of the invention. The same applies to the location and to the number of the members such as carburettors, radiators, etc.

While I have described what I at present consider preferred embodiments of my invention, it

willbeobvioustothouskilledintheartthat various changes and modifications maybe made a without departing from my invention.

What I claim is:

1. In an aircraft engine of the character described wherein air may be supplied to the cylinders directly from the atmosphere when the atmospheric pressure is of a proper value and tially compressed to said compressor, conduit means connectiing said auxiliary compressing units in series whereby the airis compressed in stages when the units are operated, cooling means to cool the air passed from each of said auxiliary compressing units before it is compressed further, and a valve-control assembly comprising a pinrality of valves and a plurality of individually operating control units providing vents which may be opened to atmosphere at the outlet of each of said auxiliary compressing units whereby the pressure of the air supplied by the particular unit is maintained substantially constant while the unit is operating, and a plurality of turbines individually operable and connected respectively to the auxiliary compressing units with each turbine being connected to be operated by the exhaust gases of the engine. and valve means to control the discharging oi the gases directly to atmosphere or selectively to said turbines whereby said turbines individually operate their respective auxiliary compressing units.

2. Apparatus as described in claim 1 wherein said turbines are serially related and wherein the entire stream of exhaust gases may be passed through said turbines.

3. Apparatus as described in claim 1 wherein the engine is provided with a main exhaust passage leading to the atmosphere and an auxiliary exhaust passage connected with a turbine, and

exhaust control means to discharge exhaust gases into the auxiliary exhaust passage during the initial portion of the exhaust stroke and to discharge exhaust gases into the main passage during the remainder of the exhaust stroke.

4. In combination with an internal combustion aircraft engine of the character wherein the air which is simplied with the fuel is to be maintained at a substantially predetermined value,an auxiliary.compressing assembly to control the pressure of the air supplied to the en ine and to compress the air'when the pressure of the 7 a surrounding atmosphere is below the pressure riestotheexhaustpipeiromtheenginetothm' then desired for the engine comprising, a plurality or individually operable rotary compressin units, a plurality of coolers, conduit means connecting said individual compressing units and said coolers in series, valve means including a plurality oi individually operable valves positioned respectively to vent the discharge from each compressing unit to atmosphere. a plurality of pressure responsive control imits connected respectively to each of said valves and each responsivetotheairpressureontheinnersideoiits valve whereby its valve is moved toward its open position when the air pressure in the conduit is above a certain predetermined value, a plurali y of individually operable turbines connected in seby expand the exhaust gases in stages when the turbines are operating, means turbines respectively to said c units wherein a compressor is provided to supply air when atmospheric pressure is below the desired value, the combination with the compressor oi a plurality of auxiliary compressing units adapted to be driven individually and to supply air parwhereby the compressing units are individually operated by controlling the operation of the respective turbines, valve means in the conduit carrying the exhaust gasesto each turbine whereby the turbine is rendered inoperable by opening the valve and discharging the gases directl to theatmosphere. and control means to control the P- eration of the last-named valve means. 

